Vehicle access system

ABSTRACT

The invention relates to an access unit for communicating with a further access unit to control access to a vehicle. The access unit comprises at least a first transmitter for transmitting a polling signal; and at least a first receiver for receiving an authentication signal from the further access unit in response to the polling signal. At least the first transmitter is a first ultra-wideband transmitter and at least the first receiver is a first ultra-wideband receiver. The invention also relates to a vehicle access system which is a combination of the access and further access units. The invention also relates to methods of operating a vehicle access system and a vehicle access unit.

RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.14/355,652, filed May 1, 2014, which is a 35 U.S.C. § 371 national stageapplication of PCT Application No. PCT/EP2012/072895, filed on Nov. 16,2012, which claims priority from Great Britain Patent Application No.1119792.8 filed on Nov. 16, 2011, the contents of which are incorporatedherein by reference in their entireties. The above-referenced PCTInternational Application was published in the English language asInternational Publication No. WO/2013/072489 A1 on May 23, 2013.

TECHNICAL FIELD

The present invention relates to a vehicle access system for providingpassive access to a vehicle. The vehicle access system has particularapplication for motor vehicles. Aspects of the invention relate to anaccess unit, to a system, to a method and to a vehicle.

BACKGROUND OF THE INVENTION

It is known to provide passive entry and passive starting (PEPS) systemsfor motor vehicles. The vehicle user typically carries a key fob whichcan communicate with a base station in the vehicle. The key fob remainsin a very low power state to conserve its internal battery. Upon receiptof an initiating trigger (for example when a vehicle door handle isoperated), the base station emits a powerful Low Frequency (LF)electromagnetic field, the energy from which wakes up the key fob usinga charge pump technique. Once awake, the key fob can then respond to achallenge using Radio Frequencies (RF). The key fob sends a responsesignal which is validated by the base station to authenticate the keyfob. If the key fob is authenticated, the base station actuates a doorlock to unlock the door.

The energy required from the vehicle to generate the LF field isconsiderable, which is why a trigger is universally employed to beginthe process. Moreover, the consequence of using an initiating trigger isthat the whole sequence of validating the key fob's identity andunlocking the vehicle has to be extremely short to avoid a customerexperiencing a delay in the vehicle's response. To help avoid any suchdelay, a fast-release motor can be provided to unlock the door toprovide seamless operation as if the vehicle was already unlocked.

The present invention attempts to address or ameliorate at least some ofthe above problems associated with known vehicle access systems.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides an access unit forcommunicating with a further access unit to control access to a vehicle,the access unit comprising:

-   -   at least a first transmitter for transmitting a polling signal;        and    -   at least a first receiver for receiving an authentication signal        from the further access unit in response to said polling signal;    -   wherein at least the first transmitter is a first ultra-wideband        transmitter and at least the first receiver is a first        ultra-wideband receiver.

The use of an ultra-wideband transmitter for transmitting the pollingsignal is advantageous in that the power required to generate thepolling signal is very low. Because of the low power demand, it ispossible for the polling signal to be used to initiate communicationbetween the access unit and the further access unit. In this way, it isnot necessary for there to be an initial trigger, such as the useroperating the door handle. Rather, communication can be initiatedwirelessly. Thus, any delay experienced by the user in opening thevehicle door can be eliminated without the need to incur the additionalcost of a fast-release motor in the door. Furthermore, because thepolling signal is transmitted over such a wide bandwidth, it isresistant to multi-path fading which adversely affects conventionalnarrow band schemes in ‘crowded’ RF environments. This enables the useof the polling signal to reliably initiate communication between theaccess unit and the further access unit in situations where there arelots of reflections.

At least the first transmitter may be configured operatively to transmitthe polling signal continually during an operating period to initiatecommunication between the access unit and the further access unit.

At least the first transmitter may be configured to pulse the pollingsignal with a time interval between transmissions. Alternatively, atleast the first transmitter may be configured to transmit the pollingsignal continuously such that there is no time interval betweentransmissions. In either case, at least the first transmitter can besaid to be activated for the duration of the operating period totransmit the polling signal, i.e. whether the polling signal iscontinuously transmitted or continually transmitted with a time intervalbetween transmissions, whereas, outside of the operating period, atleast the first transmitter may be deactivated.

At least the first transmitter may be configured, in use, to modify thelength of the time interval between transmissions of the polling signalin response to parameters determined from the communication between theaccess unit and the further access unit.

At least the first transmitter may be configured: to increase the timeinterval between transmissions of the polling signal in response to anincrease in the distance between the access unit and the further accessunit; and/or to reduce the time interval between transmissions of thepolling signal in response to a reduction in the distance between theaccess unit and the further access unit.

At least the first transmitter may be configured to modify the length ofthe time interval between transmissions of the polling signal independence on the distance between access unit and the further accessunit, wherein said distance is determined based on the time of flight ofcommunications between the access unit and the further access unit. Itis a particular advantage of ultra-wide communications that it ispossible to distinguish between signals which travel along a direct pathbetween transmitter and receiver and those which follow non-directpaths. Accordingly, this allows the distance between the access unit andthe further access unit to be established with a high degree ofaccuracy, much more so than distance measurements in conventionalnarrow-band systems which typically rely on radio signal strengthintensity (RSSI) measurements.

The access unit may be a portable unit for communicating with a furtheraccess unit installed in a vehicle.

At least the first transmitter may stop transmitting the polling signalif the access unit is stationary for a predetermined period of time. Inother words, the operating period, during which the first transmitter isactivated and transmission of the polling signal occurs, may beterminated if the access unit remains stationary for a predeterminedperiod of time.

The access unit may comprise a motion sensor for outputting anactivation signal to start at least the first transmitter transmittingthe polling signal when the access unit is moved. Thus, when at leastthe first transmitter is activated by the activation signal, a newoperating period starts and transmission of the polling signalcommences.

In another aspect, the present invention provides a vehicle accesssystem comprising an access unit as described above in combination witha further access unit, wherein the further access unit comprises:

-   -   at least a second receiver for receiving the polling signal from        the access unit; and    -   at least a second transmitter for transmitting an authentication        signal;    -   wherein at least the second transmitter is operatively        configured to transmit the authentication signal in response to        the polling signal received from the access unit; and    -   wherein at least the second transmitter is a second        ultra-wideband transmitter and at least the second receiver is a        second ultra-wideband receiver.

The further access unit may comprise a controller for authenticating aresponse signal transmitted from the access unit in response to saidauthentication signal.

The controller may be configured to initiate unlocking of at least onevehicle door when the distance between the access unit and the furtheraccess unit is less than or equal to a threshold range; and/or thecontroller may be configured to initiate locking of at least one vehicledoor when the distance between the first access unit and the furtheraccess unit is greater than or equal to a threshold range.

The controller may be configured to determine a distance between theaccess unit and the further access unit; and/or the controller may beconfigured to determine a direction of the access unit in relation tothe further access unit; and/or the controller is configured to initiatethe unlocking of at least one vehicle door on the side of the vehicleproximal the access unit.

The distance between the access unit and the further access unit may bedetermined based on the time of flight of communications between theaccess unit and the further access unit.

The controller may be configured to generate an alert signal if avehicle door is partially or completely open; and/or the controller maybe configured to generate a shut-down signal to disable the access unit.

In a further aspect, the present invention provides a method ofoperating a vehicle access system, the method comprising:

-   -   transmitting a polling signal from an access unit; and    -   transmitting an authentication signal from a further access unit        upon receipt of said polling signal;    -   wherein the polling signal and the authentication signal are        ultra-wideband signals.

The polling signal may be transmitted continually during an operatingperiod and contact between the access unit and the further access unitmay be initiated upon receipt of the polling signal by said furtheraccess unit.

Optionally, at least one vehicle door is unlocked when the distancebetween the access unit and the further access unit is less than orequal to a threshold range; and/or at least one vehicle door is lockedwhen the distance between the access unit and the further access unit isgreater than or equal to a threshold range.

The method may comprise determining the distance between the access unitand the further access unit based on the time of flight ofcommunications between the access unit and the further access unit.

In still another aspect, the present invention provides a method ofoperating an access unit for controlling access to a vehicle, the methodcomprising: transmitting a polling signal continually to initiatecommunication between the access unit and a further access unit, whereinthe polling signal is an ultra-wideband signal.

The polling signal may be pulsed and a time interval is introducedbetween pulses, and the time interval may be modified in response tochanges in a measured parameter relating to said access unit and/or saidfurther access unit. The length of the time interval may be modified independence on the distance between the access unit and the furtheraccess unit, the method comprising determining the distance between theaccess unit and the further access unit based on the time of flight ofcommunications between the access unit and the further access unit.

In a further aspect, the present invention provides a vehicle having anaccess unit or a system, or adapted to perform a method as describedabove.

According to one aspect of the present invention there is provided afirst access unit for communicating with a second access unit to controlaccess to a vehicle, the first access unit comprising at least a firsttransmitter for transmitting a polling signal and at least a firstreceiver for receiving an authentication signal from the second accessunit in response to said polling signal, wherein at least the firsttransmitter is configured operatively to transmit the polling signalcontinually to initiate communication between the first access unit andthe second access unit.

By transmitting the polling signal continually, the first access unitcan establish communication with the second access unit to facilitateautomated operation. In prior art systems, an initiating trigger, forexample issued when a door handle is operated, is required to activatethe system. The arrangement of the present invention whereby the pollingsignal is transmitted continually allows passive operation without aninitiating trigger.

At least the first transmitter is configured to transmit the pollingsignal continually. When the second access unit receives the pollingsignal, an interrogation cycle can be initiated automatically. Inresponse to the polling signal, the second access unit can transmit anauthentication signal. The authentication can, for example, be achallenge signal to prompt transmission of a response signal from thefirst access unit. If the second access unit receives an appropriateresponse signal, the first access unit is authorized to control accessto the vehicle. The interrogation cycle between the first and secondaccess units is passive and does not require user input.

The polling signal could be continuous. However, to conserve power, thepolling signal can be pulsed with a time interval between transmissions.The time interval between transmissions of the polling signal can begreater than or equal to: 0.5 seconds, 1 second, 2 seconds, 3 seconds, 5seconds or 10 seconds. An increased time interval can help to conservepower.

Furthermore, at least the first transmitter can be configured to adjustthe time interval between transmissions of the polling signal inresponse to measured parameters. For example, the time interval betweenrepetitions of the polling signal can be increased as the distancebetween the first access unit and the second access unit increases.Conversely, the time interval between transmissions of the pollingsignal can be reduced as the distance between the first access unit andthe second access unit decreases. Alternatively, the time intervalbetween transmissions of the polling signal can be adjusted depending onthe speed with which the first access unit and the second access unittravel towards or away from each other.

At least the first transmitter could, for example, access a look-uptable comprising a set of threshold values for selecting the timeinterval between transmissions of the polling signal. The look-up tablecan specify the time interval between transmissions based on themeasured distance between the first access unit and the second accessunit. The look-up table can specify the time interval betweentransmissions based on the speed at which the second access unit istravelling towards or away from the vehicle. The look-up table can bestored in memory, such as Read Only Memory (ROM).

To conserve power, the polling signal can be transmitted continuallyduring a predetermined time period. The time period can be greater thanor equal to: 6 hours, 12 hours, 24 hours, 5 days, 10 days, 15 days or 30days. The time period may be shortened if the first access unitdetermines that a battery power level has dropped below an operatingthreshold.

The first access unit can comprise a plurality of said firsttransmitters and/or a plurality of said first receivers. An antenna isconnected to at least the first transmitter and/or at least the firstreceiver.

The first access unit could be provided in a base unit in the vehicleand the second access unit could be a portable, such as a key fob.Alternatively, the first access unit can be portable, for example a keyfob, to be carried on the person of a user. The second access unit canbe provided in the vehicle, for example in a base unit.

According to another aspect of the present invention there is provided avehicle access system comprising a first access unit as described hereinin combination with a second access unit. The second access unit cancomprise: at least a second receiver for receiving the polling signalfrom the first access unit; and at least a second transmitter fortransmitting an authentication signal. At least the second transmittercan be operatively configured to transmit the authentication signal inresponse to the polling signal received from the first access unit.

The second access unit can comprise a plurality of said secondtransmitters and/or a plurality of said second receivers. An antenna isconnected to at least the second transmitter and/or at least the secondreceiver.

The second access unit can comprise a controller for authenticating aresponse signal transmitted from the first access unit in response tosaid authentication signal. The second controller can, for example,comprise an electronic control unit.

The controller can be configured to determine a distance between thefirst access unit and the second access unit. The time of flight (ToF)of a transmission between the first access unit and the second accessunit can be used to determine the distance between the first access unitand the second access unit. The distance can be determined by measuringthe time taken between transmitting an authentication signal andreceiving a signal from the first access unit. There are variousalgorithms in the art for performing suitable ranging measurements.

The controller can be configured to determine a direction of the firstaccess unit in relation to the second access unit. The time of flight(ToF) of a transmission between the first access unit and the secondaccess unit can be used to determine a direction of the first accessunit in relation to the second access unit. The direction can, forexample, be determined by measuring the distance between at least thefirst transmitter/receiver in the first access unit and at least thesecond transmitter/receiver in the second access unit. A triangulationalgorithm can then be employed to calculate the position of the firstand second access units in relation to each other.

The second access unit can be configured to track the position of thefirst access unit. The second access unit can perform vector analysis tomeasure both the speed and direction of travel of the first access unit.

The controller can be configured to initiate locking and/or unlocking ofat least one vehicle door. The controller can initiate unlocking of oneor more vehicle doors when the distance between the first access unitand the second access unit is less than or equal to a threshold range.The controller can be configured to initiate locking of at least onevehicle door when the distance between the first access unit and thesecond access unit is greater than or equal to a threshold range.

The controller could be configured to unlock said at least one vehicledoor only when the first access unit is moving towards the second accessunit. The controller could be configured to lock said at least onevehicle door only when the first access unit is moving away from thesecond access unit.

The controller can be configured to initiate the unlocking of at leastone vehicle door on the side of the vehicle proximal the first accessunit. For example, the controller could be configured to unlock only thevehicle door closest to the first access unit. By determining theposition of the first access unit in relation to the second access unit(as described herein), the controller can determine whether the firstaccess unit is on the right hand side or the left hand side of thevehicle. The door(s) on that side of the vehicle can then be opened.

The controller can be configured to generate an alert signal if avehicle door is partially or completely open. The controller can, forexample, determine if a door is ajar and cannot be locked. The alertsignal can provide a mis-lock notification.

The controller can provide single point entry or multiple point entry tothe vehicle. In multiple point entry, all of the vehicle's doors areunlocked, for example when a user operates the door handle on a doorwhich has been unlocked by the controller. In single point entry, thevehicle doors are locked when the first access unit is detected insidethe vehicle and the doors are all closed.

The controller can be operable to disable the first access unit. Forexample, a shut-down signal can be transmitted by the second transmitterto disable the first access unit. A shut-down signal could, for example,be transmitted if the controller determines that the first access unitis stationary for a predetermined period or time; and/or in a particularlocation (for example inside the vehicle or in the glove box of thevehicle). The shut-down signal can provide an instruction to the firstaccess unit to stop transmitting the polling signal. The first accessunit could be re-activated by pressing a button. Alternatively, thefirst access unit may comprise a motion sensor, such as an accelerometeror a gyroscope, which outputs an activation signal when the first accessunit is moved. The provision of a motion sensor for controlling thefirst access unit is believed to be patentable independently.

The second access unit can be configured to transmit a status signal toprovide vehicle status information. For example, the status signal canprovide a notification that: (i) all doors have been locked; (ii) one ormore doors are open or ajar; or (iii) one or more doors cannot belocked. The first access unit can comprise display means for notifying auser of the vehicle status. For example, one or more Light EmittingDiodes (LEDs); or a display could be provided on the first access unit.

The first access unit can comprise a rechargeable battery for operatingthe first transmitter and the first receiver. The first access unit canbe docked in the vehicle to recharge the battery. The first access unitcan comprise a processor for controlling the first transmitter and/orthe first receiver. The processor can be configured to calculate adistance between the first access unit and the second access unit. Theinterval between transmission cycles for the polling signal can be setby said processor.

At least the first transmitter and at least the first receiver can becombined as at least a first transceiver. Each first transceiver canhave a first antenna. Likewise, at least the second transmitter and atleast the second receiver can be combined as at least a secondtransceiver. Each second transceiver can each have a second antenna.

The apparatus and processes described herein could be implemented usingRF frequencies. However, the inventors have recognised thatultra-wideband technology is suitable for implementing the presentinvention whereby the polling signal is transmitted continually. The useof ultra-wideband transmitters and receivers allows time of flight (ToF)to be determined for communications between the first access unit andthe second access unit. The time of flight can be employed to determinethe distance between the first access unit and the second access unit;and/or the direction of the first access unit in relation to the secondaccess unit. At least the first transmitter can be a firstultra-wideband transmitter and at least the first receiver can be afirst ultra-wideband receiver. At least the second transmitter can be asecond ultra-wideband transmitter and at least the second receiver canbe a second ultra-wideband receiver.

Ultra-wideband (UWB) technology typically has an operating frequency ofbetween 3.1 GHz and 10.6 GHz and can enable high bandwidthcommunications with low power consumption. A suitable operating protocolis provided under IEEE 802.15.4a. Furthermore, the sub-set of UWBfrequencies designated as Band Group 6 (consisting of Bands #9, #10 and#11, ranging from 7392 MHz to 8976 MHz) can be used.

According to a further aspect of the present invention there is provideda vehicle access unit for installation in a vehicle, wherein the vehicleaccess unit comprises: at least one receiver for receiving a signal froma remote access unit; at least one transmitter for transmitting anauthentication signal to said remote access unit; and a controller. Thecontroller can be configured to initiate unlocking of at least onevehicle door when the distance between the vehicle and the remote accessunit is less than or equal to a threshold range. The controller can beconfigured to initiate locking of at least one vehicle door when thedistance between the vehicle and the remote access unit is greater thanor equal to a threshold range. Alternatively, or in addition, thecontroller can be configured to determine a direction of the remoteaccess unit in relation to the vehicle. The controller can be configuredto initiate the unlocking of at least one vehicle door on the side ofthe vehicle proximal the remote access unit.

According to a still further aspect of the present invention there isprovided a method of operating a first access unit for controllingaccess to a vehicle, the method comprising: transmitting a pollingsignal continually to initiate communication between the first accessunit and the second access unit. The first access unit can be installedin the vehicle or can be portable.

The polling signal can be pulsed and a time interval can be providedbetween pulses. The time interval can be varied between pulses inresponse to measured parameters, such as the distance between the firstaccess unit and the second access unit. The present invention alsorelates to a computer program for installation on a control unit, thecomputer program being executable to cause the control unit to operatein accordance with the method described herein.

According to another aspect of the present invention there is provided amethod of operating a vehicle access system, the method comprisingtransmitting a polling signal from a first access unit and transmittingan authentication signal from a second access unit upon receipt of saidpolling signal, wherein the polling signal is transmitted continuallyand contact between the first access unit and the second access unit isinitiated upon receipt of the polling signal by said second access unit.

The first access unit could be installed in a vehicle and the secondaccess unit could be portable. Alternatively, the first access unit canbe portable and the second access unit can be installed in a vehicle.

The method can comprise tracking the position of the first access unitin relation to the second access unit.

At least one ultra-wideband transmitter can be used to transmit thepolling signal and/or the authentication signal. The polling signaland/or the authentication signal can be received by at least oneultra-wideband receiver.

The polling signal could be continuous or it could be pulsed. A timeinterval can be provided between pulses of the polling signal. The timeinterval can be modified in response to changes in a measured parameterrelating to said first access unit and/or said second access unit. Forexample, the method can comprise increasing the time interval betweentransmissions of the polling signal as the distance between the firstaccess unit and the second access unit increases. Conversely, the methodcan comprise reducing the time interval between transmissions of thepolling signal as the distance between the first access unit and thesecond access unit decreases.

The method can comprise unlocking at least one vehicle door when thedistance between the first access unit and the second access unit isless than or equal to a threshold range. The threshold range can definean authorization zone which extends at least partially around thevehicle.

The method can comprise determining the position of the first accessunit in relation to the second access unit and optionally unlocking atleast one door on the appropriate side of the vehicle.

The method can comprise locking at least one vehicle door when thedistance between the first access unit and the second access unit isgreater than or equal to a threshold range.

The method can also comprise transmitting a shut-down signal to disablethe first access unit if it is determined that the first access unit isdormant. The first access unit may be considered to be dormant if it isnot moved for a predetermined period of time; and/or is in a particularlocation (for example it is inside the vehicle or in a glove box in thevehicle).

The first access unit can be a key fob or other portable device whichcan be carried on the person of a user. The second access unit can be abase station in a vehicle. The second access unit can be connected tovehicle systems over a communication bus.

According to yet another aspect of the present invention there isprovided a first access unit for communicating with a second access unitto control access to a vehicle, the first access unit being portable andcomprising: at least a first transmitter for transmitting a pollingsignal; and at least a first receiver for receiving an authenticationsignal from the second access unit; wherein the first access unit isconfigured to disable at least the first receiver and/or at least thefirst transmitter if the first access unit remains substantiallystationary for a predetermined period of time. The first access unit canbe an electronic key, for example in the form of a key fob. Byselectively deactivating at least the first receiver and/or at least thefirst transmitter, unnecessary dialogue between the first and secondaccess units can be avoided to preserve the battery.

The position of the first access unit can be tracked by the secondaccess unit. The second access unit can transmit a deactivation signalto the first access unit if it determines that the first access unit hasbeen substantially stationary for said predetermined period of time. Thedeactivation signal could be specific to a particular first access unit,for example if more than one first access unit is in use. The firstaccess unit can be configured to stop transmitting the polling signalupon receipt of said deactivation signal.

The first access unit can further comprise a motion detector, such as anaccelerometer or a gyroscope, for detecting movement of the first accessunit. When the first access unit is moved, the motion detector cantransmit an activation signal to instruct at least the first transmitterto start transmitting the polling signal. It will be appreciated thatthe motion sensor could be configured to transmit the deactivationsignal if it determined that the first access unit had beensubstantially stationary for a predetermined period of time.

The method described herein can be implemented on a computational devicecomprising one or more processors, such as an electronic microprocessor.The processor(s) can be configured to perform computational instructionsstored in memory or in a storage device. The electronic control unitdescribed herein can comprise one or more processors configured toperform computational instructions.

Within the scope of this application it is envisaged that the variousaspects, embodiments, examples, features and alternatives set out in thepreceding paragraphs, in the claims and/or in the following descriptionand drawings may be taken independently or in any combination thereof.For example, features described in connection with one embodiment areapplicable to all embodiments unless there is incompatibility offeatures.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described, by way ofexample only, with reference to the accompanying figures, in which:

FIG. 1 shows a schematic representation of a vehicle access systemaccording to an embodiment of the present invention;

FIG. 2 shows the installation of the base station and transceivers ofthe vehicle access system in a motor vehicle;

FIG. 3 a first operating mode of the vehicle access system;

FIG. 4 illustrates a second operating mode of the vehicle access system;

FIG. 5 illustrates a third operating mode of the vehicle access system;and

FIG. 6 illustrates a fourth operating mode of the vehicle access system.

DETAILED DESCRIPTION OF AN EMBODIMENT

An access system 1 in accordance with an embodiment of the presentinvention is shown in FIG. 1. The vehicle access system 1 is configuredto provide enhanced Passive Entry and Passive Start (ePEPS) of a vehicle3. In particular, the vehicle access system 1 supports keyless accessand, optionally, remote engine start.

The vehicle access system 1 will be described with reference to thevehicle 3 which has a front right door D1, a rear right door D2, a frontleft door D3 and a rear left door D4. The vehicle 3 also has a boot lidD5 (also known as a deck lid) which can be locked/unlocked by thevehicle access system 1 but this is not described herein for the sake ofbrevity. The doors D1-D4 each have a lock mechanism and an externalhandle; and the front doors D1, D3 each have a folding door mirror. Thelock mechanisms each comprise a door lock switch to provide a lockingsignal to indicate the status of the respective lock mechanism.

The vehicle access system 1 comprises a base station 5 to be installedin the vehicle 3 to provide a Remote Function Actuator (RFA) for thevehicle 3. The base station 5 comprises an electronic control unit 7 anda first rechargeable battery 9. The first rechargeable battery 9provides a dedicated power supply for the base station 5 to enableindependent operation. The base station 5 further comprises first,second and third ultra-wideband transceivers 11, 13, 15. The firsttransceiver 11 is provided proximal the electronic control unit 7. Thesecond and third transceivers 13, 15 are positioned in the vehicle 3remote from the electronic control unit 7 and connected via a dedicatedlocal interconnect network (LIN) 17. The transceivers 11, 13, 15 eachhave an integrated antenna.

The base station 5 is connected to the vehicle systems (denotedgenerally by the reference numeral 19) via a CAN bus 21. The basestation 5 can thereby receive the locking signals from the door lockswitches; and control operation of the door lock mechanisms. The CAN bus21 can also be employed to convey instructions from the electroniccontrol unit 7 to the engine control unit to enable/disable passiveengine starts.

The vehicle access system 1 further comprises a key fob 23 having aremote ultra-wideband transceiver 25 and a second rechargeable battery27. The key fob 23 is portable and is typically carried by the user. Asdescribed herein, the key fob 23 communicates with the base station 5 toenable passive entry to the vehicle.

The base station 5 further comprises a connector dock 29 for receivingthe key fob 23. The connector dock 29 has a port 31 to enablecommunication between the base station 5 and the key fob 23. A chargingconnection 33 is also provided in the connector dock 29 to charge thesecond rechargeable battery 27 when the key fob 23 is docked. Abi-colour light emitting diode 35 is provided in the connector dock 29to indicate the status of the key fob 23 (for example to indicate thatthe second rechargeable battery 27 is charging or is fully charged). Thecharging connection 33 is connected to a power supply unit (PSU)provided in the base station 5. An external charge port 37 for the baseunit 35 is provided for charging the first battery 9.

The installation of the vehicle access system 1 is illustrated in FIG.2. The base station 5 and the first transceiver 11 are located at therear of the vehicle 3 and the second and third transceivers 13, 15 arelocated in the upper part of the vehicle (typically in the roof) on theright and left sides respectively of the vehicle 3. As illustrated bydashed lines in FIG. 2, the transceivers 11, 13, 15 communicate with thekey fob 23. The distance from each of the first, second and thirdtransceivers 11, 13, 15 to the remote transceiver 25 can be determinedby measuring transmission and/or response time (for example, time offlight for a signal transmission) thereby allowing the position of thekey fob 23 in relation to the vehicle 3 to be determined throughtriangulation. The use of ultra-wideband frequencies (typically greaterthan 3 GHz) allows the position of the key fob 23 to be tracked with arelatively high degree of accuracy.

The remote transceiver 25 transmits a polling signal which, whenreceived by the first transceiver 11, initiates communication betweenthe base station 5 and the key fob 23. Upon receipt of the pollingsignal, the first transceiver 11 responds by transmitting a challengesignal. The challenge signal is received by the key fob 23 and promptsthe transmission of a response signal. The electronic control unit 7validates the response signal.

If the response signal is authenticated, the electronic control unit 7continues to communicate with the key fob 23 and tracks its position inrelation to the vehicle 3. Moreover, provided the challenge/responsesequence is completed successfully, the electronic control unit 7 willprovide access to the vehicle 3 subject to operating criteria beingsatisfied. If the response signal is not authenticated, the electroniccontrol unit 7 will not unlock the vehicle 3.

The polling signal is transmitted continually by the remote transceiver25 so that communication with the base station 5 is initiated by the keyfob 23. Accordingly, the vehicle access system 1 can initiate achallenge/response cycle without the need for user interaction, such asactuating a door handle.

To conserve the second battery 27, the polling signal is transmitted foran operating period of thirty (30) days. The transmission of the pollingsignal is stopped if the key fob 23 does not establish communicationwith the base station 5 during the operating period. A button providedon the key fob 23 can be pressed to re-commence transmission of thepolling signal after said operating period has expired.

In the presently described embodiment, the polling signal is nottransmitted continuously. Rather, the polling signal is repeated duringthe operating period with a time interval between transmission cycles(pulses), i.e. the polling signal is transmitted continually during theoperating period. The time interval between the transmission cycles canbe modified in response to measured parameters. For example, the timeinterval between transmissions can be modified depending on the measureddistance between the vehicle 3 and the key fob 23. If the key fob 23 isclose to the vehicle 3, the time interval can be reduced to one (1)second. Conversely, if the key fob 23 is relatively far away from thevehicle 3, the time interval can be increased to five (5) seconds, forexample.

The base station 5 and the key fob 23 can communicate with each otherover a range of at least 20 meters and an authorization zone 39 having aradius of 2 meters is defined around the vehicle 3. When the electroniccontrol unit 7 determines that the key fob 23 is inside theauthorization zone 39 it automatically unlocks one or more of thevehicle's doors D1-D4. Conversely, when the electronic control unit 7determines that the key fob 23 is outside the authorization zone 39, itautomatically locks the vehicle's doors D1-D4.

Operating modes of the vehicle access system 1 will now be described byway of example. In the illustrated operating modes, the key fob 23 iscarried on the person of the user and the movements of the user areillustrated by a set of footprints 41. The process for authenticatingthe key fob 23 is the same as described above and is common to each ofthe operating modes. In particular, the remote transceiver 25 transmitsa polling signal which initiates an authentication cycle with the firsttransceiver 11. The base station 5 transmits a challenge signal whichtriggers transmission of a response signal from the key fob 23. Theelectronic control unit 7 validates the response signal and, ifsuccessful, the base station 5 tracks the range and position of theauthenticated key fob 23. If the authentication cycle is notsuccessfully completed, for example due to an incorrect response signalbeing sent from the key fob 23, the doors D1-D4 will not be unlocked andthe vehicle 3 will not respond to the key fob 23.

A first operating mode is illustrated in FIG. 3 in which the vehicleaccess system 1 operates to unlock the doors D1-D4 on the side of thevehicle 3 on which the user approaches with the key fob 23. Havingauthenticated the key fob 23 the base station 5 tracks its range andposition. In the illustrated example, the electronic control unit 7determines that the key fob 23 is on the right hand side of the vehicle3. Once the base station 5 determines that the key fob 23 is within theauthorization zone 39, the electronic control unit 7 automaticallygenerates a door unlock signal to unlock both doors D1, D2 on the righthand side of the vehicle 3. The door unlock signal is transmitted viathe CAN bus 21 and the front right door D1 and the rear right door D2are unlocked when the key fob 23 enters the authorization zone 39. Asthe door is unlocked before the user operates the respective doorhandle, in normal operating conditions it is envisaged that there wouldbe no perceptible delay when the user operates the door handle.

When the user operates the door handle on either the front right door D1or the rear right door D2, either a single-point entry (SPE) or amultiple-point entry (MPE) can be initiated. In a single-point entry,the electronic control unit 7 generates control signals to lock all ofthe doors D1-D4 when the key fob 23 is detected inside the vehicle 3 andall of the doors D1-D4 have been closed. In a multiple-point entry, theelectronic control unit 7 generates control signals to unlock all of theother doors in the vehicle 3 when the door handle of either the frontright door D1 or the rear right door D2 is operated. It will beappreciated that the front left door D3 and the rear left door D4 willbe unlocked if base station 5 determines that the key fob 23 enters theauthorization zone 39 on the left hand side of the vehicle 3.

Only when the door handle of one of the unlocked doors D1-D4 is operatedis an indication provided that the doors have been unlocked, for exampleby flashing the side repeaters and/or extending the door mirrors. Ifnone of the door handles are operated, no indication is provided thatone or more of the doors D1-D4 have been unlocked.

A second operating mode is illustrated in FIG. 4 in which the vehicleaccess system 1 detects a walk-past scenario in which the user does notoperate a door handle. As before, the base station 5 authenticates thekey fob 23 as it approaches the vehicle. The base station 5 tracks theposition of the key fob 23 and determines that the user is approachingfrom the rear of the vehicle 3 on the right hand side. When the vehicleaccess system 1 detects that the key fob 23 has entered theauthorization zone 39, a door unlock signal is transmitted to unlock thefront right door D1 and the rear right door D2.

This is the same operating procedure as described above for the firstmode of operation, but in this case the user does not operate the doorhandle on either of the doors D1, D2. Instead, the user walks past thevehicle 3. The vehicle access system 1 determines when the key fob 23leaves the authorization zone 39 and a door lock signal is transmittedto lock the front right door D1 and the rear right hand door D2. Thevehicle 3 does not provide a visual indication when the doors D1, D2 areunlocked or subsequently locked.

A third operating mode is illustrated in FIG. 5 in which the vehicleaccess system 1 operates automatically to lock the doors D1-D4 when theuser walks away from the vehicle 3. The user exits the vehicle 3carrying the key fob 23 and closes the vehicle doors D1-D4. In thepresent example, the user exits the vehicle 3 through the front rightdoor D1 and then closes it. The user then walks away from the vehicle 3carrying the key fob 23 with them. The vehicle access system 1determines when the key fob 23 has left the authorization zone 39 andtransmits a door lock signal to lock the doors D1-D4. The vehicle 3 isthereby secured automatically without the user activating the key fob 23or taking any action other than walking away from the vehicle 3. Asecurity protocol to comply with industry standards, for example thosespecified by Thatcham®, would typically be undertaken for the automaticlocking of the doors D1-D4.

Under normal operating conditions, the automatic locking of the vehicle3 does not double-lock the vehicle. Rather, the vehicle 3 would only bedouble-locked if the user specifically selected this locking mode, forexample via a control panel in the vehicle 3.

A fourth operating mode is illustrated in FIG. 6 in which the vehicleaccess system 1 operates in a mis-lock scenario. This mode is similar tothe third operating mode described above insofar as the user exits thevehicle 3 through the front right door D1 and closes the door D1 beforewalking away from the vehicle 3. The vehicle access system 1 againdetermines when the key fob 23 leaves the authorization zone 39.However, as illustrated in FIG. 6, the rear left door D4 is ajar and theelectronic control unit 7 determines that the door cannot be locked (aso-called mis-lock).

To avoid the user leaving the vehicle 3 in an unsecure state (as mayotherwise occur if they had not noticed that the rear left door D4 wasajar) the electronic control unit 7 transmits an alert signal to the CANbus 21 and a notification is provided to the user. For example, the CANbus 21 may illuminate the side repeaters and/or provide an audiblewarning to notify the user that the doors D1-D4 have not all beenlocked. When the rear left door D4 is closed, the vehicle access system1 will lock the door D4 to secure the vehicle 3.

The vehicle access system 1 can optionally also provide keyless enginestarting for the vehicle 3. By using the ranging data from thetransceivers 11, 13, 15, the electronic control unit 7 can determinewhen the key fob 23 is inside the vehicle 3. A control signal can betransmitted to the engine control unit, via the CAN bus 21, to permitkeyless engine starting when a Start button is pressed.

The vehicle access system 1 according to the present invention can befurther refined. In particular, the electronic control unit 7 can beconfigured to transmit a status signal to the key fob 23. For example,if the base station 5 detects a mis-lock scenario, the status signal mayinstruct the key fob 23 to generate a first user alert. Equally, thestatus signal may instruct the key fob 23 to generate a second useralert (which is different from the first user alert) when the vehicle 3has been locked. The first and/or the second user alert could beprovided instead of, or in addition to, any notification provided by thevehicle 3. The key fob could comprise an audio, optical or haptic outputfor indicating the vehicle status. For example, the key fob 23 couldcomprise one or more of the following: LED(s), a text screen or avibrating mechanism.

The key fob 23 is also provided with one or more buttons to allow a userto trigger locking/unlocking of the vehicle doors from outside of theauthorization zone 39.

The ultra-wideband (UWB) transceivers 11, 13, 15, 25 described hereinare compliant with IEEE802.15.4a protocol.

The vehicle access system 1 can monitor time of flight (ToF)communications between the base station 5 and the key fob 23 to provideimproved security, for example to protect against a relay-stationsecurity attack.

A door unlock override switch can be provided to unlock the doors D1-D4in the event of an emergency.

The skilled person will understand that various changes andmodifications can be made to the vehicle access system 1 describedherein without departing from the spirit and scope of the presentinvention. For example, a welcome lights function could be supported byilluminating an interior and/or exterior vehicle light when the key fob23 enters the authorization zone 39.

Although the vehicle access system 1 has been described with referenceto the key fob 23 transmitting the polling signal, the system could alsooperate if the base station 5 transmitted the polling signal.

The key fob 23 could be provided with a motion sensor, such as agyroscope or an accelerometer, to detect movement. The key fob 23 couldbe disabled if the base station 5 determines that it has been stationaryfor a predetermined period of time. For example, the base station 5could transmit a disable signal to deactivate the transceivers 11, 13,15, 25. Alternatively, the transceivers 11, 13, 15, 25 could be disabledautomatically if they do not receive an authorisation signal for apredetermined period of time. The key fob 23 could be awakened by anactivation signal from the motion sensor when it detects movement.

In the embodiment of the vehicle access system 1 described above, thebase station 5 comprises three transceivers 11, 13, 15. As mentionedpreviously, with such an arrangement, in which the transceivers 11, 13,15 are disposed at spaced apart locations within the vehicle 3, it ispossible to use the transmission and/or response times forcommunications sent between the key fob 23 and each of the transceivers11, 13, 15 to determine the position of the key fob 23 relative to thevehicle 3. In more detail, with the base station 5 and the firsttransceiver 11 located toward the rear of the vehicle and the second andthird transceivers 13, 15 disposed within the roof (on respective leftand right sides), the position of the key fob 23 in a horizontal planearound the vehicle 3 can readily be determined, i.e. as shown in theplan view of FIGS. 2 to 6. However, with the second and thirdtransceivers 13, 15 disposed in the vehicle roof, and therefore lying inthe same horizontal plane, there may be situations in which it is notpossible to readily determine the position of the key fob 23 in avertical plane, i.e. in a direction normal to the plan views of FIGS. 2to 6. Being able to accurately determine the position of the key fob 23in a three-dimension space around the vehicle 3 may be particularlyuseful in certain situations, for example when the vehicle is parked ina multi-level or multi-storey car park. In such situations it ispossible that the driver, having exited the vehicle 3 may move toanother level of the car park above or below the vehicle 3, but still beclose enough to the vehicle to be within the authorisation zone,resulting in one or more of the vehicle doors being unlocked.Accordingly, in a further embodiment of the invention, the vehicleaccess system 1 may comprise a fourth transceiver which is disposedwithin the vehicle at a location which is spaced apart in a verticaldirection from both the plane of the vehicle roof and the horizontalplane in which the base station 5 lies. For example, the fourthtransceiver could be mounted in the vehicle dashboard on the vehiclecentre line. With this configuration, the height of the key fob 23relative to the vehicle 3 can readily be determined. Accordingly, if itis determined that the key fob 23 is disposed sufficiently above orbelow the vehicle, such as in the example of the multi-level car park,the electronic control unit 7 may not unlock the vehicle doors even whenthe key fob 23 would otherwise be judged to be within the authorisationzone.

Moreover, it will be appreciated that it is not necessary for a vehicleaccess system according to the present invention to provide all of theoperating modes described herein. Rather, one or more of the operatingmodes could be embodied in an access system in accordance with thepresent invention.

The invention claimed is:
 1. An access unit configured to control accessto a vehicle via communication with a further access unit, the accessunit comprising: a first transmitter configured to transmit a pollingsignal; and a first receiver configured to receive an authenticationsignal from the further access unit in response to said polling signal;wherein the first transmitter is a first ultra-wideband transmitter andthe first receiver is a first ultra-wideband receiver; wherein the firsttransmitter is configured to pulse the polling signal with a timeinterval between transmissions; wherein a distance between the accessunit and the further access unit is continuously measured, and whereinthe first transmitter increases the time interval between transmissionsof the polling signal as the distance between the access unit and thefurther access unit increases, and/or decreases the time intervalbetween transmissions of the polling signal as the distance between theaccess unit and the further access unit decreases; and wherein thefurther access unit comprises a controller that is configured toinitiate unlocking of at least one vehicle door when the distancebetween the access unit and the further access unit is less than orequal to a threshold range, and wherein the controller is configured toinitiate locking of at least one vehicle door when the distance betweenthe access unit and the further access unit is greater than or equal tothe threshold range.
 2. The access unit of claim 1, wherein the firsttransmitter is configured operatively to transmit the polling signalcontinually during an operating period to initiate communication betweenthe access unit and the further access unit.
 3. The access unit of claim1, wherein the access unit is a portable unit, and wherein the furtheraccess unit is installed in the vehicle.
 4. The access unit of claim 3,wherein the first transmitter stops transmitting the polling signal ifthe access unit is stationary for a predetermined period of time.
 5. Theaccess unit of claim 4, further comprising a motion sensor foroutputting an activation signal to start the first transmittertransmitting the polling signal when the access unit is moved.
 6. Avehicle access system comprising the access unit of claim 1 incombination with a further access unit, wherein the further access unitcomprises: a second receiver configured to receive the polling signalfrom the access unit; and a second transmitter configured to transmit anauthentication signal; wherein the second transmitter is operativelyconfigured to transmit the authentication signal in response to thepolling signal received from the access unit; and wherein the secondtransmitter is a second ultra-wideband transmitter and the secondreceiver is a second ultra-wideband receiver.
 7. The vehicle accesssystem of claim 6, wherein the further access unit comprises acontroller that is configured to: continuously measure the distancebetween the access unit and the further access unit; or continuouslydetermine a direction of the access unit in relation to the furtheraccess unit.
 8. The vehicle access system of claim 7, wherein thecontroller is configured to initiate unlocking of at least one vehicledoor on a side of the vehicle proximal the access unit.
 9. The vehicleaccess system of claim 7, wherein the controller is configured togenerate an alert signal if a vehicle door is partially or completelyopen.
 10. The vehicle access system of claim 7, wherein the controlleris configured to generate a shut-down signal to disable the access unit.11. An access unit configured to control access to a vehicle viacommunication with a further access unit, the access unit comprising: afirst transmitter configured to transmit a polling signal; and a firstreceiver configured to receive an authentication signal from the furtheraccess unit in response to said polling signal; wherein the firsttransmitter is a first ultra-wideband transmitter and the first receiveris a first ultra-wideband receiver; wherein the first transmitter isconfigured to pulse the polling signal with a time interval betweentransmissions; wherein the first transmitter is configured to modify alength of the time interval between transmissions of the polling signalin response to speed with which the access unit and the further accessunit travel towards or away from each other determined from thecommunication between the access unit and the further access unit,wherein the speed is determined based on a time of flight ofcommunications between the access unit and the further access unit, thefirst transmitter being configured to set the length of the timeinterval in dependence on the determined speed; and wherein the furtheraccess unit comprises a controller that is configured to initiateunlocking of at least one vehicle door when a distance between theaccess unit and the further access unit is less than or equal to athreshold range, and wherein the controller is configured to initiatelocking of at least one vehicle door when the distance between theaccess unit and the further access unit is greater than or equal to thethreshold range.
 12. A method of operating a vehicle access system, themethod comprising: transmitting a polling signal from an access unit;transmitting an authentication signal from a further access unit uponreceipt of said polling signal; continuously measuring a distancebetween the access unit and the further access unit; wherein the pollingsignal and the authentication signal are ultra-wideband signals; whereinthe polling signal is pulsed and a time interval is introduced betweenpulses, and wherein the time interval increases as the distance betweenthe access unit and the further access unit increases, and/or whereinthe time interval decreases as the distance between the access unit andthe further access unit decreases; and unlocking at least one vehicledoor when the distance between the access unit and the further accessunit is less than or equal to a threshold range, and locking at leastone vehicle door when the distance between the access unit and thefurther access unit is greater than or equal to the threshold range. 13.The method of claim 12, wherein the polling signal is transmittedcontinually during an operating period and contact between the accessunit and the further access unit is initiated upon receipt of thepolling signal by said further access unit.
 14. A vehicle having theaccess unit of claim 1 or claim
 11. 15. A vehicle having the vehicleaccess system of claim 6.